1. Field of the Invention
Embodiments relate to transmission/reception of data. More particularly, embodiments relate to a clock-data recovery circuit, a multi-port receiver including the clock-data recovery circuit, and a method of recovering clocks and data.
2. Description of the Related Art
As a chip-to-chip data rate expands to a radio frequency (RF) band, a system may be seriously affected by skew between input pins. Skew may be caused by a routing path, a parasitic element, noise, and so forth. To compensate for skew of each input pin, clock information from data stream at a reception end may be extracted. Thus, a clock-data recovery (CDR) circuit has been adopted in an inter-chip transceiver.
A typical CDR circuit includes a sampler, a voltage-controlled oscillator, a phase-frequency detector, and a charge pump/loop filter. When operated as a binary-type CDR circuit, the CDR circuit repeatedly receives a data signal to detect data transition points.
In a typical multi-port receiver, CDR circuits are provided for each input pin of the multi-port receiver. The CDR circuits independently recover each of clocks based on the input data signals and generate output data signals in accordance with a multi-phase clock signal, based on a reference clock signal.
Accordingly, the multi-port receiver has to activate CDR circuits and receive signals having minimum data transition point from the transmitter to maintain skew information of each input pin even in a standby mode. If the multi-port receiver deactivates the CDR circuits and data is not transferred to the receiver in the standby mode, a phase locking time of the CDR circuit is increased when the multi-port receiver is woken up from the standby mode to an active mode, thereby increasing a latency of the transmitter/receiver system.
When a same reference clock signal is shared between a receiver and a transmitter, e.g., in a chip-to-chip data transmission/reception, the CDR circuit may be practically limited to phase alignment or deskewing. As such, when phase alignment or deskewing alone is required, implementation of an independently driven CDR unit for each input pin may not be practical. Further, a capacitor included in a loop filter of each CDR unit generally occupies a large area, thus using individual CDR units for each pin may be unsuitable to portable systems.